Energy optimization and comparative study of pre- and post-fractionator extractive dividing wall column for the CO2–ethane azeotropic process

• Two arrangements is proposed for extractive DWC based on pre- and post- fractionator.
• Operating parameters are optimized to minimize energy demand.
• The pre-fractionator design showed the best performance in comparison to others.

Two possible extractive dividing-wall column (DWC) arrangements are explored to find the potential benefits derived from thermally coupled distillations in separation of a mixture including the CO2–ethane azeotrope with a low boiling point. It is shown that the process including pre-fractionator in the DWC design in its optimized state leads to 51.6% reduction in total duties in comparison with the conventional process. Furthermore, a comparison between conventional extractive distillation columns and the new DWC process is made in terms of cost estimation, CO2 removal efficiency and CO2 emission reduction. Remarkable, the results clearly show that DWC process is interesting/feasible and the novel proposed DWC alternative reduces the steam requirements by 41% and the equipment costs by 31%.

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